By eliminating tasks and projects that represent 80% of the effort but yield only 20% of the outcome (and are the source of stress), one can focus on the high-impact 20% that yields 80% of results.
"This allows me to focus on the 20% again that yields the best outcome overall. Or really, I guess in other words, I'd become this master at optimizing the 80% of my work that really led to 20% of the outcome. And when most of my stress, my headache is tied to that 80%, it becomes a no-brainer just to cut it out."